In the past two decades, the prevalence of overweight has almost tripled among adolescents. Findings from numerous studies have demonstrated associations between physical activity and obesity;decreased physical activity may lead to obesity and obesity appears to lead to further declines in physical activity levels. Furthermore, studies have found that there is a steep decline in physical activity among adolescents, in particular among girls. The proposed study aims to evaluate the impact of New Moves, an innovative school based program for inactive high school girls who are overweight or at risk for becoming overweight due to low levels of physical activity. The primary research hypothesis to be tested is that girls in the intervention condition will significantly decrease their percent body fat as compared to girls in the control condition. Secondary research hypotheses to be tested are that girls in the intervention condition will significantly increase their level of physical activity and improve the quality of their dietary intake as compared to girls in the control condition. In addition, the study will assess program impact on a range of related behavioral, personal, and socio-environmental factors. New Moves is an all-girls alternative to the regular high school physical education classes. The program will be offered during school hours and girls will receive credit for participation. Throughout a 16-week school semester, girls will participate in physical activity four times a week and in discussions on nutrition and social support one time a week. In addition, the program will include: 1) individual guidance via face-to-face and telephone sessions;2) structured booster activities throughout a one-year period following completion of the New Moves class;and 3) family outreach activities. Program impact will be evaluated over an 18-month period using a randomized controlled study design with six intervention and six control high schools from urban and suburban schools in the Minneapolis/St. Paul area of Minnesota. The study population will include 360 girls (an average of 30 girls from each school). The proposed study period is five years.